Oral Health in Adults: Social Gradients and Correlation With Cardiovascular Health

Title:

Oral health in adults: predictors, social gradients and correlation with cardiovascular health in women and men. Date: 24.02.2023

1\. Excellence 1.1 State of the art, knowledge needs and project objectives Non-communicable diseases (NCD) are rising in prevalence globally because of aging, refined diets and sedentary lifestyle. Two of the most common NCDs in humans, caries and periodontitis (here named oral diseases), contribute substantially to years lived with disability in age-standardized prevalence rates worldwide. Cardiovascular (CV) disease (CVD) is the leading cause of death and years lived with disability globally. Co-presence of CVD and oral diseases is therefore common, and an association between oral diseases and CVD has been observed in epidemiological studies.

Mechanisms linking oral diseases to CVD include transfer of oral pathogen bacteria and pro-inflammatory mediators to other organs triggering immune response and systemic and vascular inflammation. Circulating inflammatory cytokines may initiate an acute-phase response in the liver with production of C-reactive protein and serum amyloid A and increased tryptophan degradation, that contribute to CV inflammation and atherosclerosis. We have demonstrated that higher serum levels of these inflammatory markers are associated with presence of hypertension and obesity in midlife in the Hordaland Health Study, and with higher risk of subsequent CVD independent of clinical risk factors. However, CVD and oral diseases also share many of the same risk factors, including hypertension, obesity, diabetes, and smoking. Since the association of oral disease with CV risk factors so far mostly has been demonstrated in cross-sectional studies, the direction of these associations has not been ascertained. These CVD risk factors lead to chronic CV inflammation which promotes atherosclerosis as well as structural and functional changes in the heart and arteries (preclinical CVD) and are all more harmful in women than men. Whether these conditions can impact development of oral diseases is not fully explored.

Socio-economic inequalities have been reported for many oral diseases. In a study in subjects older than 65 yrs from Northern Norway, severe periodontitis was more prevalent in men, smokers and subjects with low socio-economic status (SES). Thus, sex and SES may modify the association between oral diseases and CVD. It is presently unknown whether CV health in midlife, measured by CV risk factor burden, circulating inflammatory markers and SES, may impact presence and severity of oral disease in women and men later in life. It is also unknown if the structural and functional oral microbiome differ by periodontitis severity and can be associated with inflammatory biomarkers, CV risk factors and presence or absence of preclinical CVD. Finally, the association between oral diseases and preclinical CVD has to date not been explored in large studies.

The current project will explore the interface between odontology, microbiology, medicine and social science in a cohort of community dwelling adults approaching the retirement age (born in 1950-1951), in Hordaland County (now Vestland). We will combine data from the ongoing Hordaland Oral Health Survey (HUSK-T) with their data from three surveys in the longitudinal Hordaland Health Study (HUSK) performed in the period 1992-2020. A total of 2254 participants were invited to HUSK-T which was completed in 2022 with a participation rate of 63%. The project objectives will focus on the interaction of oral diseases with CV health:

1. Describe oral diseases in the cohort and their relation to quality of life in women and men. 2. Investigate the structural and functional oral microbiome in relation to periodontitis severity, CV health and systemic inflammatory biomarkers in women and men. 3. Investigate whether CV risk factors, inflammatory biomarkers and SES in midlife predict oral disease later in life in women and men. 4. Explore the associations between oral disease prevalence and severity and preclinical CVD in women and men.

1.2 Research questions and hypotheses, theoretical approach and methodology WP1A Oral health and quality of life We will describe oral health status as periodontal health or disease, tooth loss and caries experience (DMFT= decayed+missed+filled teeth) among participants in HUSK-T and test the hypothesis that oral health related quality of life is associated with oral health status in women and men.

Task 1.1 Description of oral diseases Periodontal disease Periodontitis is a common chronic inflammatory disease characterized by bone resorption, deepening of the pocket and bleeding upon probing. It is a multifactorial disease affected by interaction between subgingival microbiota, host response and environmental modifying factors. A dysbiosis in the dental biofilm results in activation of an inflammatory host response followed by tissue destruction. The tissue destruction is largely irreversible and therefore cumulative over lifetime. Social gradients are reported among periodontitis patients and they are age and area of residence dependent. Sex differences in this context have not been explored in Norway.

Methods: Periodontal examination in HUSK-T includes assessment of bleeding on probing (BOP), periodontal probing depth (PPD), and gingival recession (GR) at six sites per tooth for all teeth. PPD is registered as the distance from the marginal gingiva to the probable base of the pocket and GR as the distance from enamel cement junction (CEJ) to marginal gingiva.

Clinical attachment level (CAL) is calculated adding GR and PPD. Periodontitis is considered present if interdental CAL 1-2 mm is present at ≥ 2 non-adjacent teeth, or buccal/oral CAL ≥3 mm with PPD \> 3 mm at ≥ 2 teeth. Severity is grouped as mild, moderate and severe. Periodontal health in a reduced periodontium is clinically defined as \< 10% bleeding sites with no bleeding pockets \> 3 mm.

Dental caries and endodontic treatment In HUSK-T, caries is diagnosed based on clinical and radiologic findings and root-filled teeth detected in the panoramic radiograph. Methods: Caries is registered on tooth surfaces and classified as decayed (d) from 1-5. For root caries; only active lesions are registered.

Tooth loss: as part of the oral health status registration, missed teeth are calculated as the total number minus number of lost teeth. Periodontitis and caries are the two most important causes of loss of teeth. Number of teeth as an outcome is strongly associated to income in older adults.

Task 1.2. Self-reported oral health Little is known about how oral conditions impact the quality of life of older women and men in Norway. Some studies have reported associations between tooth loss and oral health related quality of life (OHRQoL), but the association to periodontal disease is less documented. Methods: Self-reported data related to the conceptual model of Gilbert et al. (17) (i.e. OHRQoL, self-perceived oral health, symptoms, access to dental care services and socio-demographic factors) are collected by questionnaires. For measurement of OHRQoL, the eight item oral impacts on daily performances inventory (OIDP) has proven appropriate as a discriminative and descriptive measure in cross-sectional studies. We previously (19) used the OIDP scale in a national sample of adults and found it to be reliable and valid in the Norwegian context. All eight items are included in our questionnaire and OIDP frequency SC score will be performed.

WP1B Structural and functional oral microbiome in periodontitis and relation to CV health We will test the hypotheses that 1) The microbiome composition in subgingival plaque vary between participants with severe, moderate, and mild periodontitis and can be linked to the prevalence of hexa-acylated lipo-polysaccharide (LPS) producing bacteria; 2) The microbiome composition varies with presence of CV risk factors or/and preclinical CVD in women and men.

Task 1.3 We will investigate if the structural and functional oral microbiome differ by periodontitis severity and Task.1.4 can be associated to inflammatory biomarkers in the kynurenine-tryptophan pathway, CV risk factors (see WP2) and presence or absence of preclinical CVD (see WP3) in women and men.

The oral bacteria community composition in health has been found to be rather stable over time. Research has suggested that the transition from health to disease may be attributed to a shift in the global balance of the microbial flora rather than to the appearance of individual bacteria. Porphyromonas gingivalis, a bacterium known to be important for human periodontal disease, has been detected in atherosclerotic lesions, where they may act as pro-atherogenic stimuli. Further, atherosclerotic susceptible mice exposed to P. gingivalis developed advanced atherosclerotic lesions. It has been reported that low gut (21) microbiome diversity correlates with higher arterial stiffness in woman, but overall there are very few studies that have explored the association between microbiome composition, CV risk factors and preclinical CVD. The pro-inflammatory function of the oral microbiome in periodontitis in such setting has never been investigated. The lipid A component of LPS in the cell wall of all gram-negative bacteria trigger the immune response in the host, and five lipid chains has 100-fold less inflammatory activity than the lipid A with six lipid chains. Using the well-conserved lipid A structure, the bacteria can be classified based on which lipid A coding gene they carry. No previous studies have linked Lipid A functions to periodontal disease and severity, nor to systemic inflammation, CV risk factors or preclinical CVD outcomes.

Methods: Bacterial composition will be characterized in subgingival plaque samples from participants with mild, moderate, and severe periodontitis and from healthy participants (e.g. 200 participants in each periodontitis severity group and 400 healthy participants). For bacterial quantification we will use qPCR for bacterial DNA yield, 16S rRNA Illumina HiSeq sequencing and reduced metagenome sequencing (RMS) for bacterial determination. To assign taxonomy we will use the Human Oral Microbiome Database (www.homd.org).The reduced metagenome sequences can be applied in the functional annotation model to identify genes that code for the different lipid As. The output data can then be imported into any statistical framework.

WP2 A CV risk factors in midlife: impact on oral health status in later life. We will test the hypothesis that CV risk factors and markers of immune system activation measured in midlife predict oral health later in life, and whether these associations differ between sexes.

Task 2.1 Prospectively explore the association of CV risk factors (HUSK-2 and -3) with presence of oral diseases (HUSK/T) and test if these associations differ between sexes.

Associations between oral diseases like periodontitis, caries and tooth loss and CV risk factors have been suggested from smaller studies and meta-analyses (24, 25), but many of them are based on self-reported information. Periodontitis, caries, hypertension and diabetes also share some common risk factors, including obesity. Thus, CV risk factor burden may influence oral health. Prospective studies, using objective measures for CV risk factors and oral health later in life are missing and warranted. Sex differences in prevalence of CV risk factors and CVD are well described, but it remains unknown whether sex differences exist in the association between oral and CV health.

Task 2.2 Explore underlying inflammatory pathways of the association of CV risk factors with prevalence and severity of oral diseases test if the strength of these associations differs between sexes.

Little is known about underlying pathways explaining the associations of oral health with CV risk factors and CVD. Periodontitis has been postulate